1. Field of the Invention
The present invention relates to a projector apparatus for projecting a projection light obtained by passing a white light from a light source through a color splitting device or a color wheel means, Digital Micromirror Device™ (hereinafter referred to as “DMD™”) and an optical means for projection onto a screen to form thereon a desired picture, that is to say, a projector apparatus of the so-called Digital Light Processing™ type (hereinafter referred to as “DLP™ type”).
More particularly, the present invention relates to a projector apparatus in which color adjustments of the projection light such as an adjustment of the color temperature and an adjustment of the white balance can be achieved more easily and accurately.
2. Prior Art
It is very important for a projector apparatus of the DLP type to have the desired color temperature and white balance which represent the quality of the projection light. When such a projector apparatus of the DLP type is used, it is therefore necessary to sense and adjust the color temperature and the white balance of the projection light to thereby achieve the desired color temperature and white balance. It has been known, for example, from Japanese Patent Application Laid-Open No. 2001-188196 (page 1 and FIG. 1, in particular) a projector apparatus of the DLP type which is arranged to be able to sense (or detect) the color temperature and white balance of the light for projection and to adjust them based on the sensing results when necessary.
In such a DLP-type projector apparatus, a great deal of heat is generated from the light source when the apparatus is in use. The generated heat may bring about a change in temperature in the body of the apparatus, leading to deformation of the apparatus body. In such a DLP-type projector apparatus, in addition, the optical systems are subjected to a secular change in their transmittance, reflectance and the like as the apparatus is used over time.
Thus, the DLP-type projector apparatus has a problem that the color temperature and the white balance, which represent the quality of the projection light in terms of perceived colors of image, may change whereby the predefined colors are not maintained, with the result that images cannot be obtained with the colors originally intended.
To solve such a problem, the color temperature and while balance of the projection light may be sensed and adjusted to the predetermined values when necessary. The DLP-type projector apparatus disclosed in the above-described reference has such a structure that those of the reflection lights from the DMD which are reflected in a direction different from the direction of projection (OFF lights) are sensed to obtain information about the projection light, based on which the color temperature and white balance are adjusted.
In a DLP-type projector apparatus, when sensing the color temperature and white balance of the projection light to adjust them to the predefined values as occasion demands, it will be most appropriate and accurate to perform such sensing on the screen onto which the light is projected to form an image. In actuality, however, the screen on which an image is formed by the projected light and the projector apparatus are a large distance apart from each other, which causes another problem that it is necessary to provide a means of a considerable scale for feeding the sensing results back to projector apparatus. Also, the sensing of the color temperature and/or white balance of the projection light in the DLP-type projector apparatus should be done exclusively for the projection light and thus need be performed in a condition where no other lights exist, which makes the work necessary for sensing the color temperature and/or white balance on the screen and for adjusting them very complicated and troublesome and thus renders the problem more serious.
When detecting the color temperature and/or white balance of the projection light of the projector apparatus, the detection of the color temperature and/or white balance must be carried out in a dark condition since accurate color temperature and/or white balance cannot be detected if any light other than the projection light is present. Hence, the detection of the color temperature of the projection light and the adjustment of the color temperature based on the detection results are carried out in a dark condition, which makes the work necessary therefor very complicated and troublesome and thus renders the problem more serious.
The projector apparatus disclosed in the above-described reference has such a structure that those of the light beams from the DMD which are reflected in a direction different from the direction of projection are detected to obtain information about the light. This structure makes it possible to carry out the detection of the color temperature and/or white balance of the light within the apparatus body and can thus circumvent the problem that the means necessary for adjusting the color temperature and/or while balance of the projection light becomes large in scale as well as the problem that the work itself for carrying out the detection of the color temperature and/or white balance is troublesome.
With the projector apparatus of the above-described structure, however, the sensing of the color temperature and white balance is performed using a light (OFF light) different from the projection light, i.e., a light obtained without passing through the optical means for projection (i.e., projection optics) which is liable to affect the color temperature and white balance of the projection light due to its change in temperature and/or secular change. Therefore, the projector apparatus of this structure has a problem that accurate sensing and secure adjustment of the color temperature and/or white balance cannot be achieved.
In recent years, viewers of projector apparatuses are becoming more and more sensitive to colors, tonality, hue and the like of the projected picture. If a picture whose color temperature and white balance are not accurately maintained is recognized as a picture whose color temperature and white balance are properly maintained, the value of the picture work itself projected by that projector apparatus will be harmed, which will render the problem more serious.
The modern projector apparatus is required to have various features which may include such a feature that the position of image projected on the screen can be shifted. A projector apparatus which can cause the position of image on the screen to be shifted may be constructed such tat the projection optics is slidable relative to the apparatus body in a perpendicular relation to its optical axis. It is necessary for a projector apparatus of the above-described structure to have such an arrangement that the color temperature and/or the white balance can be detected even when the projection optics is slid relative to the apparatus body in a perpendicular relation to its optical axis. More specifically, it is necessary for the projector apparatus to be able to detect the color temperature and/or white balance of the projection light from the projection optics even when the projection light from the projection optics moves relative to the apparatus body in a perpendicular relation to the optical axis of the projection optics.